This application is a U.S. National Phase Application of PCT International Application PCT/JP99/02715 filed May 24, 1999.
The present invention relates to a range finder device for measuring a three-dimensional shape of an object.
A range finder device for performing three-dimensional shape measurement based on triangulation of projected light and an observed image, such as real-time operable range finder device shown in, for example, FIG. 40 has been proposed.
In FIG. 40, reference numerals 101A and 101B denote laser light sources having slightly different wavelengths; 102, a half mirror for synthesizing laser light from the laser light sources having the different wavelengths; 103, a light source control part for controlling light intensity of the laser light source; 104, a rotary mirror for scanning laser light; 105, a rotation control part for controlling the rotary mirror; 106, an object; 107, a lens for forming an image on a CCD; 108A and 108B, light wavelength separation filters for separating light having wavelength from the laser light source; 109A and 109B, CCDs for picking up a monochromatic image; 109C, a CCD for picking up a color image; 110A and 110B, signal processing parts for a monochromatic camera; 111, a signal processing part for a color camera; 112, a distance calculation part for calculating a distance or a shape of an object from intensity of laser light photographed by CCDs 109A and 109B; and 113, a control part for adjusting synchronization of the entire device. Hereinafter, the description will be made of the operation of a range finder device thus configured.
The laser light sources 101A and 101B emit laser light having slightly different wavelengths. This laser light is a line light having a light cross-section perpendicular to the scanning direction of a rotary mirror (to be described later), and becomes a line light in the perpendicular direction when a rotary mirror scans in the horizontal direction.
FIG. 41 shows wavelength characteristics for these two light sources. The reason why two light sources having close wavelengths to each other are used resides in the fact that it is less influenced by dependency of the reflection factor of the object on a wavelength. The laser light emitted from the laser light sources 101A and 101B is synthesized by the half mirror 102, and is scanned on the object 6 by the rotary mirror 104.
Scanning of the laser light is performed when the rotation control part 105 drives the rotary mirror 104 at one field period. At that time, light intensities of both light sources is varied as shown in FIG. 42(a) within one field period. The variations in the laser light intensity are synchronized by driving of the mirror angle, whereby the intensities of those two laser lights are monitored by CCD 109A and 109B to calculate the light intensity ratio, making it possible to measure time at one scanning period. If the light intensity is Ia/Ib, as shown in, for example, FIG. 42(b), the scanning time is measured to be t0, and a rotation angle (xcfx86) of the rotary mirror 104 can be determined from the measured value.
The ratio of the intensities of those two laser lights and the mirror angle (that is, angle of the object as viewed from the light source side) are caused to have a one-to-one correspondence therebetween, whereby the distance or shape of the object can be calculated from a ratio of signal levels on which light from both light sources has been photographed in a distance calculation part (to be described later), in accordance with the principle of triangulation.
The lens 107 forms an image of the object on CCDs 109A, 109B and 109C. The light wavelength separation filter 108A transmits light in wavelength of the light source 101A, and reflects light in another wavelength. The light wavelength separation filter 108B transmits light in wavelength of the light source 101B, and reflects light in another wavelength. As a result, reflected light from the light sources 101A and 101B from the object is photographed by the CCDs 109A and 109B, and light of another wavelength is photographed by the CCD 109C as a color image.
The light source A signal processing part 101A and light source B signal processing part 110B perform similar signal processing to the output from the CCDs 109A and 109B. The color camera signal processing part 111 performs an ordinary color camera signal processing to the output from the CCD 109C.
The distance calculation part 112 calculates a distance for each pixel using the signal level ratio, base length and coordinate values of pixels which have been photographed by the CCDs 109A and 109B for wavelength of each light source.
FIGS. 43(a) and (b) are explanatory views useful for graphically illustrating the distance calculation. In the figures, the reference character O denotes a center of the lens 107; P, a point on the object; and Q, a position of an axis of rotation of the rotary mirror. Also, for brevity, the position of the CCD 109 is shown turned around on the object side. Also, assuming the length of OQ (base length) to be L, an angle of P as viewed from Q in the XZ plane to be xcfx86, an angle of P as viewed from O to be xcex8, and an angle of P as viewed from O in the YZ plane to be xcfx89, the three-dimensional coordinate of P can be calculated by the following formula (1) from the graphical relation.
Z=D tan xcex8 tan xcfx86/(tan xcex8+tan xcfx86)xe2x80x83xe2x80x83(1)
xe2x80x83X=Z/tan xcex8
Y=Z/tan xcfx89
The xcfx86 in the formula (1) is calculated by the light intensity ratio of laser light sources 101A and 101B monitored by the CCDs 109A and 109B, as described above, and xcex8 and xcfx89 are calculated from coordinate values of pixels. Of the values shown in the formula (1), if all of them are calculated, the shape will be determined; and if only Z is determined, the distance image will be determined.
On the other hand, for photography of a place where light from the light source cannot be directly irradiated onto an object, there has been known a camera which uses an optical fiber. For example, in endoscopes to be used for examining the interior of a human body, there is a gastrocamera and the like. In the case of the gastrocamera, the inner walls of the stomach are normally irradiated by light irradiation from the optical fiber, and reflected light from the inner wall portion is received by another optical fiber which is guided by an external camera part, and this is two-dimensionally processed to display a normal image on a monitor.
As a conventional object extraction method, the technique called xe2x80x9cChroma keyxe2x80x9d used in broadcasting stations is generally used.
This method arranges an object in front of a studio set configured by the background of a single color (blue) for photographing, and judges that the blue portion is the background and any portions other than it as an attention object.
In such a conventional configuration as described above, however, a modulated light source and light source sweeping means are indispensable, and since mechanical operations are included, the reliability of the device is low and the device is expensive.
Also, although the laser element is normally modulated for use, the output and wavelength of the laser element vary depending upon the temperature, and, therefore, it is difficult to obtain stable measurements.
Also, as in case of the conventional endoscope or the like, for photography in a place. where light from the light source cannot be directly irradiated onto an object, it is difficult to determine whether or not there is any projecting region, because the image is of two-dimensional data in a camera using the optical fiber.
The present invention has been achieved in light of such problems, and aims to provide a stable range finder device free from any mechanical operations, at a low cost.
It is another object of the present invention to provide a range finder capable of measuring a distance of an object in a place where light from a light source cannot be directly irradiated onto the object.
It is further another object of the present invention to provide a camera which is simple in configuration and compact in size.
That is, the present invention is a range finder device, for measuring, when a plurality of projected lights, having radiation patterns whose light intensity differs three-dimensional space-wise, are irradiated onto an object from a light source on a time-sharing basis to image-pick up reflected light of the projected light from the object with a camera, a distance using the light intensity of an image picked up.
In an exemplary embodiment of the present invention, with respect to each of a plurality of surfaces including the center of the light source and the center of a lens, there is obtained, in advance, relation between an angle of each projected light from the light source and light intensity in each surface.
In an exemplary embodiment of the present invention, at the time of actual distance measurement, light intensity of each pixel of the camera is measured, and on the basis of the light intensity thus measured, and relation between the angle and the light intensity on a, predetermined surface corresponding to a coordinate position of the pixel measured, there is obtained the angle corresponding to the light intensity of the predetermined pixel thus measured.
In an exemplary embodiment of the present invention, on the basis of the light intensity measured, the angles obtained, and further two-dimensional coordinate position information on the predetermined pixel on the image, a distance to the object is calculated.
Further, the present invention is a range finder device, that includes a light source, a first optical fiber for guiding light to be emitted from the light source, light distribution means for dividing light guided by the first optical fiber into a plurality of courses, and a plurality of second optical fibers with one end connected to the light distribution means. The second optical fibers irradiate the light divided from an aperture at the other end thereof onto the object. The range finder device also includes image pickup means for receiving reflected light of the irradiated light to acquire image data of the object, and distance calculation means for calculating a distance to the object on the basis of the image data. Intensity of light to be irradiated onto the object from the other end of each of the plurality of second optical fibers has a distribution which is different.
Further, the present invention is a camera for shape measuring or object extracting, having light-emitting means for irradiating an object with projected light having a specified radiation pattern, and for picking up reflected light of the light-emitting means from the object to obtain a depth image using light intensity of the image picked up. The camera has a structure such that a distance between the light-emitting means and an image-pickup lens is variable, and the interval between the light-emitting means and the image-pickup lens can be sufficiently large during use of the camera.